1. Field of the Invention
The present invention is directed to mid-infrared (mid-IR) lasers, that is, lasers operating in the region of about 2 to 8 .mu.m. More particularly, the present invention is directed to n-type cladding layers which efficiently confine holes in such lasers.
2. Description of Related Art
Present mid-range IR laser diodes comprise GaInAsSb/AlGaAsSb layers, where the GalnAsSb alloy is the active layer and the AlGaAsSb alloy is the cladding layer. However, these laser diodes suffer from several disadvantages. First, these laser diodes require the use of tellurium (or other Group VI) as the dopant element, which is not a preferred dopant used in III-V molecular beam epitaxial (MBE) growth processes. Second, accurate control of the flux ratio of As:Sb and substrate temperature, which affect quaternary composition, are required for growth of useful devices. Third, the laser diodes are limited to wavelengths shorter than 4.2 .mu.m (for unstrained active layers), which limits their usefulness in certain applications.
Thus, there remains a need for a mid-IR laser which avoids most, if not all, of the foregoing problems.